ITU-T protocols H.248 and Q.1950 specify the control of “Media Gateways,” which are commonly referred to as MGWs in cellular mobile radio networks and fixed networks, by media gateway controllers (MGCs). Protocol Q.1950 “Bearer independent Call Bearer Control Protocol” (CBC) is used in conjunction with the BICC protocol Q.1902.4 already specified by the ITU-T. These protocols can also be used for 3GPP applications. Media Gateways commonly perform functions such connecting load connection sections (for transmission of load data such as voice, text, multimedia data) of telecommunications networks, and can also convert between various codings, such as G.711 or AMR voice codings. In this document, load connection section termination, also refered to herein as termination, is taken to be the termination of a section of a network connection which is switched through the MGW for data such as voice or multimedia (sound or picture) at this MGW. Through this termination, the MGW sends and/or receives data belonging to the load connection. In voice usage of protocols H.248 and Q.1950 a load connection section termination corresponds to a “termination”.
The above-mentioned protocols allow existing load connections to be changed, by selecting another coding for example. The signaling used between MGC and MGW (protocols H.248 and Q.1950) is designed so that each termination in the MGW is changed independently of the other each termination in the MGW is changed independently of the other terminations connected with it within the MGW. For example the MGW can be instructed to use another coding at this termination, or to transmit and/or receive no data, which may indicate deactivation of this termination at the MGW and/or isolation of this termination at the MGW.
The MGW does not know when changing a termination whether other terminations connected by it to this termination will subsequently be changed. Therefore, when changing a termination, the MGW must immediately take measures if it is connected with other terminations. In voice usage of protocols H.248 and Q.1950, terminations connected to each other within an MGW are in what is known as a shared “context” and different codings are produced that use what is known as transcoding to convert these codings into one another. In special cases however the coding of all terminations connected to each other in the MGW which lie in the same “context” should be changed almost simultaneously, for example, within the framework of what is known as BICC “codec modification” or “codec renegotiation” (see Q.1902.4), via which the coding of existing voice connections can be changed.
3GPP also uses said BICC procedures to switch over existing load connections between load data types such as voice and multimedia data (i.e. a combination of voice and pictures in a shared coding). The MGC can recognize such situations on the basis of what is known as “Call Control” signaling e.g. Q.1902.4. Since the signaling of the MGC occurs sequentially at the MGW, an almost simultaneous switchover of all connected terminations within an MGW results in possibly undesired operating behavior. An example of such undesirable behavior may occur if the MGW briefly activates a transcoder which is then almost immediately deactivated again thereby generating unnecessary operational load in an MGW and reducing the throughput. It would be acceptable, but to date has not been technically possible, to briefly interrupt the connection. In addition the MGW may establish, on changing the first termination, that it cannot convert the new coding of this termination into the coding used at the other termination(s). This can, for example, occur if the changeover is to be between a voice connection and a multimedia connection or a general data connection. The MGW in this case would reject the change of the load connection using H.248/Q.1950 signaling.